JP6185894B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as a copying machine, a printer, a fax machine, or a multifunction machine includes a fixing device that fixes a toner image on a recording medium such as paper.

  For example, Patent Document 1 discloses a fixing belt (see “Heating Belt 39” in Patent Document 1) and a pressure member that presses against the fixing belt to form a fixing nip (see “Pressure Belt 36” in Patent Document 1). ) And a heat source for heating the fixing belt (see “heater lamp 52” in Patent Document 1).

JP 2009-258203 A

  In the fixing device configured as described above, when the rotation of the fixing belt stops, the portion of the fixing belt that is closest to the heat source is heated by the heat source, and the fixing belt is overshooted (overheated). There is a fear.

  In the fixing device configured as described above, in the first region of the fixing belt (the region through which the first size recording medium passes), heat is taken away by the first size recording medium, whereas the fixing belt is used. In the second region (region provided outside the first region), heat is not taken away by the recording medium of the first size, so that the second region of the fixing belt may be overheated.

  In view of the above circumstances, an object of the present invention is to prevent the fixing belt from overshooting and the second region of the fixing belt from being overheated when rotation of the fixing belt is stopped.

  The fixing device according to the present invention includes a fixing belt having a first area through which a recording medium of a first size passes and a second area provided outside the first area, and a fixing nip in pressure contact with the fixing belt. A pressure member that forms a heat source, a heat source that radiates radiant heat toward the fixing belt, and the heat source from the heat source without blocking radiant heat from the heat source toward a portion of the first region that is closest to the heat source. A first blocking position that blocks radiant heat toward a portion of the second region that is closest to the heat source, a portion of the first region that is closest to the heat source, and a portion of the second region. A first moving member that is movably provided between a first retraction position that does not block radiant heat toward a portion that is closest to the heat source, and a portion that is closest to the heat source in the first region from the heat source And said A second blocking position for blocking radiant heat directed to a portion of the two regions closest to the heat source, a portion of the first region closest to the heat source from the heat source, and the second region of the second region. A second moving member that is movably provided between a second retracted position that does not block the radiant heat toward the portion closest to the heat source, the first moving member is held at the first blocking position, and the second A first holding position for holding the moving member at the second retracted position, and a second holding position for holding the first moving member at the first retracted position and holding the second moving member at the second blocking position. And a holding member movably provided therebetween.

  By adopting such a configuration, the holding member is moved to the first holding position, so that the radiant heat from the heat source toward the portion of the first area closest to the heat source is not blocked and the second area is cut from the heat source. It becomes possible to block the radiant heat toward the portion closest to the heat source. Along with this, it is possible to heat the first region while suppressing the second region from overheating.

  On the other hand, when the rotation of the fixing belt is stopped, the holding member is moved to the second holding position, so that the portion closest to the heat source in the first region and the heat source in the second region are moved from the heat source. It is possible to block radiant heat toward the closest part. Along with this, it is possible to suppress overshooting of the fixing belt.

  The holding member holds the first moving member at the first retracted position and holds the second moving member at the first holding position when the holding member is at an intermediate holding position between the first holding position and the second holding position. 2 You may hold | maintain in a retracted position.

  By adopting such a configuration, by moving the holding member to the intermediate holding position, the part closest to the heat source in the first region and the part closest to the heat source in the second region from the heat source. The first region and the second region can be heated at the same time without blocking the radiant heat.

  The fixing device outputs a first detection result when the holding member is in either the first holding position or the second holding position, and a driving source capable of rotating in the forward / reverse direction to rotate the holding member. And a detection unit that outputs a second detection result when the holding member is in the intermediate holding position, and the detection unit outputs the first detection result in a state in which the drive source is rotated in the forward direction. The holding member determines that the holding member is in the first holding position, and the holding member is moved when the detection unit outputs the first detection result with the drive source rotated in the reverse direction. And a control unit that determines that the holding member is in the intermediate holding position when it is determined that the holding member is in the second holding position and the detection unit outputs the second detection result.

  By adopting such a configuration, it is possible to determine the position of the holding member based on the combination of the rotation direction of the single drive source and the detection result of the single detection unit. Therefore, the fixing device can be simplified, reduced in cost, and reduced in size.

  The detection unit is a PI sensor including a light emitting unit and a light receiving unit, and the holding member blocks a light path from the light emitting unit to the light receiving unit in a state where the holding member is in the first holding position. One blade portion and a second blade portion that blocks the optical path from the light emitting portion to the light receiving portion in a state where the holding member is in the second holding position may be provided.

  By adopting such a configuration, it is possible to reliably detect whether the holding member is in the first holding position or the second holding position with a simple configuration.

  When the holding member rotates from the intermediate holding position to the first holding position, the first blade portion presses the first moving member, and the first moving member moves from the first retracted position to the first blocking position. And when the holding member rotates from the intermediate holding position to the second holding position, the second blade portion presses the second moving member and the second moving member moves from the second retracted position to the second holding position. You may move to the 2nd interception position.

  By adopting such a configuration, the first blade portion and the second blade portion for detecting the position of the holding member can be used together as a portion for pressing the first moving member and the second moving member. .

  The fixing device further includes a first elastic member that connects the first blade portion and the first moving member, and a second elastic member that connects the second blade portion and the second moving member, When the holding member is rotated from the first holding position to the intermediate holding position, the first blade portion pulls the first moving member via the first elastic member, and the first moving member is the first blocking member. When the holding member moves from the position to the first retracted position and the holding member rotates from the second holding position to the intermediate holding position, the second blade portion pulls the second moving member via the second elastic member. Then, the second moving member may move from the second blocking position to the second retracted position.

  By adopting such a configuration, the first moving member can be reliably restored from the first blocking position to the first retracted position, and the second moving member can be moved from the second blocking position to the second retracted position. It is possible to restore the data reliably. Moreover, even if the 1st blade | wing part moves relatively with respect to a 1st moving member by connecting a 1st blade | wing part and a 1st moving member with a 1st elastic member, a 1st blade | wing part and a 1st movement It becomes difficult to generate an excessive force between the members. Similarly, by connecting the second blade portion and the second moving member with the second elastic member, even if the second blade portion moves relative to the second moving member, the second blade portion and the second moving member. It becomes difficult to generate an excessive force between the moving members.

  The fixing device further includes an idle gear connected to the drive source, and a restriction gear connected to the holding member and meshing with the idle gear, and the holding member includes the first holding member. The gear teeth may be provided only in a range from a portion engaging with the idle gear when in the first holding position to a portion engaging with the idle gear when the holding member is in the second holding position.

  By adopting such a configuration, it is possible to reliably suppress the holding member from rotating beyond the original rotation range.

  The heat source may be disposed on an inner diameter side of the fixing belt, and the first moving member and the second moving member may be provided to be rotatable along an inner peripheral surface of the fixing belt.

  By adopting such a configuration, the space on the inner diameter side of the fixing belt can be effectively used as the arrangement space for the heat source, the first moving member, and the second moving member.

  The fixing device may further include a pressing member that presses the fixing belt toward the pressing member, and a support member that supports the pressing member.

  By adopting such a configuration, the heat capacity of the fixing device can be reduced.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, when the rotation of the fixing belt is stopped, it is possible to prevent the fixing belt from overshooting or the second region of the fixing belt from being excessively heated.

1 is a schematic diagram illustrating an outline of a printer according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. 1 is a perspective view showing a fixing device according to an embodiment of the present invention. FIG. 5 is a front view showing a state where the holding member is in an intermediate holding position in the fixing device according to the embodiment of the present invention. 4 is a perspective view showing a heater, a drive mechanism, a holding member, a PI sensor, a first moving member, and a second moving member in the fixing device according to the embodiment of the present disclosure. FIG. 6 is a perspective view illustrating a state in which the first moving member is at a first retracted position and the second moving member is at a second retracted position in the fixing device according to the embodiment of the present invention. 1 is a block diagram illustrating a control system for a fixing device according to an embodiment of the present invention. (A) is a fixing belt according to an embodiment of the present invention, the first region of the fixing belt showing a state where the first moving member is in the first retracted position and the second moving member is in the second retracted position. It is sectional drawing in the cross section which passes through. (B) is a fixing belt according to an embodiment of the present invention, the second region of the fixing belt showing a state in which the first moving member is in the first retracted position and the second moving member is in the second retracted position. It is sectional drawing in the cross section which passes through. FIG. 6 is a front view showing a state where the holding member is in a first holding position in the fixing device according to the embodiment of the present invention. FIG. 6 is a perspective view illustrating a state in which the first moving member is in a first blocking position and the second moving member is in a second retracted position in the fixing device according to the embodiment of the present invention. (A) is a fixing belt according to an embodiment of the present invention, the first region of the fixing belt showing a state where the first moving member is in the first blocking position and the second moving member is in the second retracted position. It is sectional drawing in the cross section which passes through. (B) is a fixing belt according to an embodiment of the present invention, the second region of the fixing belt showing a state in which the first moving member is in the first blocking position and the second moving member is in the second retracted position. It is sectional drawing in the cross section which passes through. FIG. 9 is a front view showing a state where the holding member is in a second holding position in the fixing device according to the embodiment of the present invention. FIG. 6 is a perspective view illustrating a state in which the first moving member is in a first retracted position and the second moving member is in a second blocking position in the fixing device according to the embodiment of the present invention. (A) is a fixing belt according to an embodiment of the present invention, the first region of the fixing belt showing a state in which the first moving member is in the first retracted position and the second moving member is in the second blocking position. It is sectional drawing in the cross section which passes through. (B) is a second region of the fixing belt showing a state where the first moving member is in the first retracted position and the second moving member is in the second blocking position in the fixing device according to the embodiment of the present invention. It is sectional drawing in the cross section which passes through.

  First, the overall configuration of the printer 1 (image forming apparatus) will be described with reference to FIG.

  The printer 1 includes a box-shaped printer main body 2, and a paper feed cassette 3 that stores paper (recording medium) is stored in a lower portion of the printer main body 2. 4 is provided. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is accommodated below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the paper discharge tray 4 above the printer body 2, and an image forming unit 8 is provided below the exposure unit 7. Yes. The image forming unit 8 is rotatably provided with a photosensitive drum 10 as an image carrier. Around the photosensitive drum 10, a charger 11, a developing device 12, a transfer roller 13, and a cleaning device are provided. The apparatus 14 is disposed along the rotation direction of the photosensitive drum 10 (see arrow X in FIG. 1).

  A paper transport path 15 is provided inside the printer main body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 configured by the photosensitive drum 10 and the transfer roller 13 is provided at a middle portion of the conveyance path 15. Is provided with a fixing device 18, and a paper discharge unit 19 is provided at the downstream end of the conveyance path 15. A reverse path 20 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing device 18 is executed. When image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 10 is charged by the charger 11, exposure corresponding to the image data is performed on the photosensitive drum 10 by laser light from the exposure device 7 (see the two-dot chain line P in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the electrostatic latent image is developed by the developing device 12 into a toner image with toner.

  On the other hand, the sheet taken out from the sheet cassette 3 by the sheet feeding unit 16 is conveyed to the transfer unit 17 in synchronization with the above-described image forming operation, and the toner image on the photosensitive drum 10 is transferred to the sheet by the transfer unit 17. Is transcribed. The sheet on which the toner image has been transferred is conveyed downstream in the conveyance path 15 and enters the fixing device 18 where the toner image is fixed on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 19 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning device 14.

  Next, the fixing device 18 will be described in detail. Hereinafter, for convenience of explanation, the front side of the sheet in FIG. 2 is the front side of the fixing device 18. Arrows Fr, Rr, L, R, U, and Lo that are appropriately attached to the drawings respectively indicate the front side, the rear side, the left side, the right side, the upper side, and the lower side of the fixing device 18. An arrow I appropriately attached to each figure indicates an inner side in the front-rear direction, and an arrow O appropriately attached to each figure indicates an outer side in the front-rear direction. An arrow Y attached to FIG. 2 indicates the sheet conveyance direction.

  As shown in FIGS. 2 and 3, the fixing device 18 includes a fixing frame 21, a fixing belt 22 accommodated in the upper part of the fixing frame 21, and a pressure roller 23 ( A pressure member), a heater 24 (heat source) disposed in a space on the inner diameter side of the fixing belt 22, a reflection member 25 disposed on the lower side of the heater 24 in a space on the inner diameter side of the fixing belt 22, and a fixing belt. A pressing member 26 disposed at a lower end portion of the inner diameter side space 22, a support member 27 disposed below the reflecting member 25 and above the pressing member 26 in the inner diameter side space of the fixing belt 22, and a fixing frame. 21, a driving mechanism 28 disposed on the front side of the driving mechanism 28, a holding member 29 disposed on the upper side of the driving mechanism 28, a PI sensor 30 (detecting unit) disposed on the upper side of the holding member 29, and the fixing belt 2. A first moving member 31 and the second moving member 32 disposed along the inner peripheral surface of, a.

  The fixing frame 21 (see FIGS. 2 to 4 and the like) includes an upper frame portion 35 and a lower frame portion 36 that are connected to each other. The upper frame portion 35 includes front and rear end plates 37Fr and 37Rr, and a top plate 38 that connects upper end portions of the front and rear end plates 37Fr and 37Rr. A circular insertion hole 40 is provided in the front end plate 37Fr of the upper frame portion 35. A first locking portion 41 is provided in the lower right portion of the insertion hole 40, and a second locking portion 42 is provided in the lower left portion of the insertion hole 40. The lower frame portion 36 includes front and rear plates 43Fr and 43Rr, and a bottom plate 44 that connects lower portions of the front and rear plates 43Fr and 43Rr.

  The fixing belt 22 (see FIGS. 2 and 3) has a cylindrical shape that is long in the front-rear direction. The fixing belt 22 has flexibility and is endless in the circumferential direction. The fixing belt 22 includes, for example, a base material layer, an elastic layer provided around the base material layer, and a release layer that covers the elastic layer. The base material layer of the fixing belt 22 is formed of a metal such as SUS, for example. The base material layer of the fixing belt 22 may be formed of a resin such as PI (polyimide). The elastic layer of the fixing belt 22 is made of, for example, silicon rubber. The release layer of the fixing belt 22 is formed of, for example, a PFA tube. In each figure, each layer (base material layer, elastic layer, release layer) of the fixing belt 22 is displayed without being particularly distinguished.

  The fixing belt 22 is rotatably supported by the upper frame portion 35 of the fixing frame 21. The fixing belt 22 is provided to be rotatable around a rotation axis A extending in the front-rear direction. That is, in the present embodiment, the rotation axis direction of the fixing belt 22 is the front-rear direction.

  As shown in FIG. 3 and the like, the fixing belt 22 includes a central region 45 (first region), an end region 46 (second region) provided outside the central region 45 (front and rear sides of the central region 45), It has. The central area 45 is an area through which a first size sheet (for example, A4 size sheet) passes. A first thermistor 47 is disposed in the central region 45. The first thermistor 47 is, for example, a non-contact type temperature sensor. The edge area 46 is an area through which a second size sheet (for example, A3 size sheet) having a width larger than that of the first size sheet does not pass through the first size sheet. A second thermistor 48 is disposed in the end region 46. The second thermistor 48 is, for example, a contact type temperature sensor.

  The pressure roller 23 (see FIG. 2 and the like) has a long cylindrical shape in the front-rear direction. A third thermistor 49 is disposed on the pressure roller 23. The third thermistor 49 is, for example, a contact type temperature sensor.

  The pressure roller 23 includes, for example, a cylindrical core member 50, an elastic layer 51 provided around the core member 50, and a release layer (not shown) that covers the elastic layer 51. Yes. The core material 50 of the pressure roller 23 is made of metal such as iron, for example. The elastic layer 51 of the pressure roller 23 is made of, for example, silicon rubber. The release layer of the pressure roller 23 is formed by, for example, a PFA tube.

  The pressure roller 23 is disposed on the lower side (outer diameter side) of the fixing belt 22. The pressure roller 23 is in pressure contact with the fixing belt 22, and a fixing nip N is formed between the fixing belt 22 and the pressure roller 23. The pressure roller 23 is rotatably supported by the lower frame portion 36 of the fixing frame 21. The pressure roller 23 is connected to a drive unit 52 (see FIG. 3) provided on the rear side of the fixing frame 21. The drive part 52 is comprised by the motor etc., for example.

  The heater 24 (see FIG. 2 and the like) is constituted by, for example, a halogen heater. The heater 24 is attached to the upper frame portion 35 of the fixing frame 21. The center B of the heater 24 is disposed slightly above the rotation axis A of the fixing belt 22 (on the side away from the pressure roller 23). Therefore, the upper end portion 45 a of the central region 45 of the fixing belt 22 is closest to the heater 24 in the central region 45 of the fixing belt 22. Similarly, the upper end portion 46 a of the end region 46 of the fixing belt 22 is closest to the heater 24 in the end region 46 of the fixing belt 22. The upper end portion 45 a of the central region 45 of the fixing belt 22 and the upper end portion 46 a of the end region 46 are located on the opposite side of the fixing nip N across the rotation axis A of the fixing belt 22 and face the fixing nip N. ing.

  The reflection member 25 (see FIG. 2 and the like) has a long shape in the front-rear direction. The reflecting member 25 is made of a metal such as bright aluminum, for example. The reflection member 25 is disposed between the heater 24 and the support member 27 and covers the upper side of the support member 27. The reflecting member 25 is bent in a U-shape toward the lower side (the pressure roller 23 side), and is bent outward from the left and right upper corners of the reflecting plate portion 53 in the left-right direction. A pair of bent plate portions 54. The reflecting plate portion 53 has a function of reflecting the radiant heat radiated from the heater 24 toward the inner peripheral surface of the fixing belt 22.

  The pressing member 26 (see FIG. 2 and the like) has a long shape in the front-rear direction. The pressing member 26 is formed of, for example, a heat resistant resin such as LCP (liquid crystal polymer). The lower surface of the pressing member 26 presses the fixing belt 22 downward (pressure roller 23 side). A fitting protrusion 55 is provided on the upper surface of the pressing member 26.

  The support member 27 (see FIG. 2 and the like) has a long shape in the front-rear direction. The support member 27 is formed of sheet metal such as SECC (galvanized steel sheet).

  The support member 27 includes a bottom plate portion 56 and a pair of side plate portions 57 bent toward the upper side (side away from the pressure roller 23) from the left and right ends of the bottom plate portion 56. A fitting hole 58 is provided in the bottom plate portion 56, and a fitting protrusion 55 of the pressing member 26 is fitted in the fitting hole 58. The bottom surface of the bottom plate portion 56 is in contact with the top surface of the pressing member 26, whereby the support member 27 supports the pressing member 26 from above.

  The drive mechanism 28 (see FIG. 4, FIG. 5, etc.) includes a drive source 60 and a drive gear train 61 disposed on the upper right side of the drive source 60.

  The drive source 60 is configured by a motor that can rotate forward and reverse. The drive source 60 includes a drive shaft 62 that protrudes upward, and a drive gear 63 is fixed to the outer periphery of the drive shaft 62.

  The drive gear train 61 includes an idle gear 64 that meshes with the drive gear 63 of the drive source 60, a regulation gear 65 that meshes with the idle gear 64, a first connection gear 66 that is provided integrally with the regulation gear 65, and a first connection. And a second connection gear 67 that meshes with the gear 66. The restriction gear 65 is provided with gear teeth 68 only in the range of 180 degrees, and no gear teeth 68 are provided in the remaining 180 degrees.

  The holding member 29 (see FIGS. 4 and 5, etc.) has an outer diameter from the support shaft 69, a driven gear 70 provided on the outer periphery of the support shaft 69, and a rear end portion (end portion on the inner side in the front-rear direction) of the driven gear 70. The first and second blade portions 71 and 72 projecting toward the side and the outer peripheral surface of the driven gear 70 are provided in an arc shape, and the base end portion of the first blade portion 71 and the base of the second blade portion 72 are provided. And a reinforcing piece 73 for connecting the end portions. The holding member 29 is provided to be rotatable about the support shaft 69.

  The driven gear 70 of the holding member 29 meshes with the second connection gear 67 of the drive gear train 61. Accordingly, the holding member 29 is connected to the drive source 60 via the drive gear train 61, and the holding member 29 can be rotated by the drive source 60. The driven gear 70 is connected to the restriction gear 65 via first and second connection gears 66 and 67.

  The first and second blade portions 71 and 72 of the holding member 29 have a sector shape. A first connection protrusion 74 is provided on the front surface (front-rear direction outer surface) of the first blade portion 71, and a second connection protrusion 75 is provided on the front surface (front-rear direction outer surface) of the second blade portion 72. Yes.

  The PI sensor 30 (see FIG. 5 and the like) includes a light emitting unit 76 that emits light and a light receiving unit 77 that receives light emitted from the light emitting unit 76.

  The first moving member 31 (see FIG. 6 and the like) has a shape that is long in the front-rear direction. The first moving member 31 includes a first main body portion 81 and a first connecting piece 82 that protrudes from the front end portion (one end portion in the front-rear direction) of the first main body portion 81 toward the front side (outward in the front-rear direction). Yes.

  The first main body 81 of the first moving member 31 is curved in an arc along the inner peripheral surface of the fixing belt 22. The first main body portion 81 is provided with an interval from the inner peripheral surface of the fixing belt 22. A rectangular recess 83 is provided at the center in the front-rear direction of the first main body 81. The position in the front-rear direction of the recess 83 overlaps with the position in the front-rear direction of the central region 45 of the fixing belt 22. As shown in FIG. 4 and the like, the lower end portion of the first main body portion 81 is locked to the first locking portion 41 of the insertion hole 40 provided in the front end plate 37Fr of the upper frame portion 35 of the fixing frame 21. Yes.

  The first connecting piece 82 of the first moving member 31 is in contact with the proximal end portion of the upper surface of the first blade portion 71 of the holding member 29. The first connection piece 82 is connected to a first connection protrusion 74 provided on the first blade portion 71 of the holding member 29 by a first coil spring 84 (first elastic member).

  The second moving member 32 (see FIG. 6 and the like) has a long shape in the front-rear direction. The second moving member 32 includes a second main body portion 85 and a second connecting piece 86 protruding from the front end portion (one end portion in the front-rear direction) of the second main body portion 85 toward the front side (outward in the front-rear direction). Yes.

  The second main body portion 85 of the second moving member 32 is curved in an arc along the inner peripheral surface of the fixing belt 22. The second main body portion 85 is provided with an interval from the inner peripheral surface of the fixing belt 22. As shown in FIG. 4 and the like, the lower end portion of the second main body portion 85 is locked to the second locking portion 42 of the insertion hole 40 provided in the front end plate 37Fr of the upper frame portion 35 of the fixing frame 21. Yes.

  The second connecting piece 86 of the second moving member 32 is in contact with the proximal end portion of the upper surface of the second blade portion 72 of the holding member 29. The second connection piece 86 is connected to a second connection protrusion 75 provided on the second blade portion 72 of the holding member 29 by a second coil spring 87 (second elastic member).

  Next, a control system for the fixing device 18 will be described.

  As shown in FIG. 7, the fixing device 18 is provided with a control unit 91. The control unit 91 is connected to the storage unit 92. The storage unit 92 stores a reference temperature T of the end region 46 of the fixing belt 22.

  The controller 91 is connected to the first thermistor 47, and the temperature of the central region 45 of the fixing belt 22 detected by the first thermistor 47 is output to the controller 91. The controller 91 is connected to the second thermistor 48, and the temperature of the end region 46 of the fixing belt 22 detected by the second thermistor 48 is output to the controller 91. The controller 91 is connected to the third thermistor 49, and the temperature of the pressure roller 23 detected by the third thermistor 49 is output to the controller 91.

  The control unit 91 is connected to the PI sensor 30, and the detection result of the PI sensor 30 is output to the control unit 91.

  The control unit 91 is connected to the drive source 60, and the drive source 60 rotates the holding member 29 based on a signal from the control unit 91. The control unit 91 is connected to the drive unit 52, and the drive unit 52 rotates the pressure roller 23 based on a signal from the control unit 91.

  The control unit 91 is connected to the heater 24, and the heater 24 is energized based on a signal from the control unit 91 to generate heat and radiate radiant heat.

  In the fixing device 18 configured as described above, when the toner image is fixed on the paper, the driving roller 52 rotates the pressure roller 23 (see arrow C in FIG. 2). When the pressure roller 23 rotates in this way, the fixing belt 22 that is in pressure contact with the pressure roller 23 is driven to rotate in the opposite direction to the pressure roller 23 (see arrow D in FIG. 2). When the fixing belt 22 rotates in this way, the fixing belt 22 slides with respect to the pressing member 26.

  In addition, when the toner image is fixed on the paper, the heater 24 is operated. When the heater 24 operates as described above, the heater 24 radiates radiant heat toward the inner peripheral surface of the fixing belt 22, and the fixing belt 22 is heated by the radiant heat. When the paper passes through the fixing nip N in this state, the paper and the toner image are heated and pressurized, and the toner image is fixed on the paper.

  Next, operations of the first moving member 31 and the second moving member 32 will be described.

  When the temperature of the end region 46 of the fixing belt 22 does not reach the reference temperature T, the first and second blade portions 71 and 72 of the holding member 29 are driven gears of the holding member 29 as shown in FIG. 70 on both the left and right sides. The position of the holding member 29 at this time is referred to as an “intermediate holding position”. In the state where the holding member 29 is in the intermediate holding position, the central portion of the gear tooth 68 of the restriction gear 65 is engaged with the idle gear 64.

  When the holding member 29 is in the intermediate holding position, the first moving member 31 is disposed on the right side of the heater 24 and the second moving member 32 is disposed on the left side of the heater 24 as shown in FIG. Yes. The position of the first moving member 31 at this time is referred to as a “first retracted position”, and the position of the second moving member 32 at this time is referred to as a “second retracted position”.

  As described above, in a state where the holding member 29 is in the intermediate holding position (a state where the first moving member 31 is in the first retracted position and the second moving member 32 is in the second retracted position), the heater 24 fixes the fixing belt 22. The radiant heat toward the upper end 45a of the central region 45 is not blocked by the first moving member 31 and the second moving member 32 as shown by the arrow E in FIG. The upper end 45a of the region 45 is reached. Further, the radiant heat from the heater 24 toward the upper end portion 46a of the end region 46 of the fixing belt 22 is blocked by the first moving member 31 and the second moving member 32 as indicated by an arrow F in FIG. Without reaching the upper end 46a of the end region 46 of the fixing belt 22. With the above operation, the central region 45 and the end region 46 of the fixing belt 22 can be heated simultaneously.

  On the other hand, when the temperature of the end region 46 of the fixing belt 22 reaches the reference temperature T with the holding member 29 in the intermediate holding position, the drive source 60 rotates by a certain amount R in the forward direction, and this rotation is the drive gear. It is transmitted to the holding member 29 via the row 61. Accordingly, as shown in FIG. 9, the holding member 29 rotates 90 degrees counterclockwise in front view. The position of the holding member 29 at this time is referred to as a “first holding position”. In a state where the holding member 29 is in the first holding position, one end portion of the gear teeth 68 of the restriction gear 65 is engaged with the idle gear 64.

  As described above, when the holding member 29 rotates from the intermediate holding position to the first holding position, the first blade portion 71 of the holding member 29 moves and presses the first connecting piece 82 of the first moving member 31. Along with this, the first moving member 31 rotates 90 degrees counterclockwise along the inner peripheral surface of the fixing belt 22 in front view and moves to the upper side of the heater 24 (see FIG. 10). The position of the first moving member 31 at this time is referred to as a “first blocking position”.

  When the holding member 29 is rotated from the intermediate holding position to the first holding position as described above, the second blade portion 72 of the holding member 29 moves and is moved via the second coil spring 87 as shown in FIG. The second moving member 32 is pulled downward. However, since the lower end portion of the second main body portion 85 of the second moving member 32 is locked to the second locking portion 42 of the insertion hole 40 of the front end plate 37Fr, the second moving member 32 does not rotate, The two-coil spring 87 extends. In the present embodiment, since the second blade portion 72 and the second moving member 32 are connected by the second coil spring 87, even if the second blade portion 72 moves relative to the second moving member 32, An excessive force is unlikely to be generated between the second blade portion 72 and the second moving member 32.

  As described above, when the holding member 29 is in the first holding position (the first moving member 31 is in the first blocking position and the second moving member 32 is in the second retracted position), the heater 24 fixes the fixing belt. As shown by an arrow G in FIG. 11A, the radiant heat toward the upper end portion 45a of the central region 45 of the 22 passes through the recess 83 of the first main body portion 81 of the first moving member 31, and the first moving member The upper end 45 a of the central region 45 of the fixing belt 22 is reached without being blocked by the first moving member 31 and the second moving member 32. On the other hand, the radiant heat from the heater 24 toward the upper end portion 46a of the end region 46 of the fixing belt 22 is blocked by the first main body portion 81 of the first moving member 31 as indicated by an arrow H in FIG. Therefore, the upper end portion 46 a of the end region 46 of the fixing belt 22 does not reach. With the above-described operation, it is possible to heat the central region 45 of the fixing belt 22 while preventing the end region 46 of the fixing belt 22 from overheating.

  When the drive source 60 rotates the fixed amount R in the reverse direction while the holding member 29 is in the first holding position as described above, the holding member 29 is rotated clockwise in front view as shown in FIG. Rotate 90 degrees to restore the intermediate holding position. Accordingly, the first blade portion 71 of the holding member 29 pulls the first connecting piece 82 of the first moving member 31 via the first coil spring 84, and the first moving member 31 is first moved from the first blocking position. Rotates to the retracted position. By adopting such a configuration, the first moving member 31 can be reliably restored from the first blocking position to the first retracted position.

  On the other hand, when the rotation of the fixing belt 22 is stopped while the holding member 29 is at the intermediate holding position, the driving source 60 rotates the fixed amount R in the reverse direction, and this rotation is performed via the driving gear train 61. Is transmitted to. Along with this, as shown in FIG. 12, the holding member 29 rotates 90 degrees in the clockwise direction when viewed from the front. The position of the holding member 29 at this time is referred to as a “second holding position”. In the state where the holding member 29 is in the second holding position, the other end portion of the gear tooth 68 of the restriction gear 65 is engaged with the idle gear 64.

  As described above, when the holding member 29 rotates from the intermediate holding position to the second holding position, the second blade portion 72 of the holding member 29 moves and presses the second connecting piece 86 of the second moving member 32. Along with this, the second moving member 32 rotates 90 degrees clockwise along the inner peripheral surface of the fixing belt 22 in front view and moves to the upper side of the heater 24 (see FIG. 13). The position of the second moving member 32 at this time is referred to as a “second blocking position”.

  When the holding member 29 rotates from the intermediate holding position to the second holding position as described above, the first blade portion 71 of the holding member 29 moves and is moved via the first coil spring 84 as shown in FIG. The first moving member 31 is pulled downward. However, since the lower end portion of the first main body 81 of the first moving member 31 is locked to the first locking portion 41 of the insertion hole 40 of the front end plate 37Fr, the first moving member 31 does not rotate, One coil spring 84 extends. In the present embodiment, since the first blade portion 71 of the holding member 29 and the first moving member 31 are connected by the first coil spring 84, the first blade portion 71 moves relative to the first moving member 31. Even so, it is difficult for an excessive force to be generated between the first blade portion 71 and the first moving member 31.

  As described above, when the holding member 29 is in the second holding position (the first moving member 31 is in the first retracted position and the second moving member 32 is in the second blocking position), the heater 24 fixes the fixing belt. Since the radiant heat toward the upper end portion 45a of the central region 45 of the 22 is blocked by the second main body portion 85 of the second moving member 32 as indicated by an arrow J in FIG. It does not reach the upper end 45a of the region 45. Further, the radiant heat from the heater 24 toward the upper end portion 46a of the end region 46 of the fixing belt 22 is blocked by the second main body portion 85 of the second moving member 32 as indicated by an arrow K in FIG. Therefore, it does not reach the upper end portion 46 a of the end region 46 of the fixing belt 22. With the above operation, it is possible to suppress the fixing belt 22 from overshooting.

  When the drive source 60 rotates the predetermined amount R in the forward direction while the holding member 29 is in the second holding position as described above, the holding member 29 is counterclockwise as viewed from the front, as shown in FIG. And 90 degrees to restore the intermediate holding position. Along with this, the second blade portion 72 of the holding member 29 pulls the second connecting piece 86 of the second moving member 32 via the second coil spring 87, and the second moving member 32 moves from the second blocking position to the second position. Rotates to the retracted position. By adopting such a configuration, the second moving member 32 can be reliably restored from the second blocking position to the second retracted position.

  As described above, the holding member 29 holds the first moving member 31 at the first blocking position and holds the second moving member 32 at the second retracted position, and the first moving member 31 at the first retracting position. An intermediate holding between the first holding position and the second holding position is provided so as to be rotatable between the first holding position and the second holding position holding the second moving member 32 at the second blocking position. In the position, the first moving member 31 is held at the first retracted position, and the second moving member 32 is held at the second retracted position.

  Next, a method for determining the position of the holding member 29 by the control unit 91 will be described.

  As shown in FIG. 4, when the holding member 29 is in the intermediate holding position, the first blade portion 71 and the second blade portion 72 of the holding member 29 are moved from the light emitting portion 76 of the PI sensor 30 to the light receiving portion 77 (FIG. 4). The optical path to (not shown) is not blocked, and the PI sensor 30 outputs the second detection result (High) to the control unit 91. In this case, the control unit 91 determines that the holding member 29 is in the intermediate holding position.

  On the other hand, when the drive source 60 rotates in the positive direction by the predetermined amount R while the holding member 29 is at the intermediate holding position, this rotation is transmitted to the holding member 29 via the drive gear train 61, as shown in FIG. Thus, the holding member 29 rotates from the intermediate holding position to the first holding position. Accordingly, the first blade portion 71 of the holding member 29 blocks the optical path from the light emitting portion 76 of the PI sensor 30 to the light receiving portion 77 (not shown in FIG. 9), and the PI sensor 30 performs the first detection result. (Low) is output to the controller 91. In this case, the control unit 91 determines that the holding member 29 is in the first holding position.

  On the other hand, when the driving source 60 rotates by the predetermined amount R in the reverse direction while the holding member 29 is in the intermediate holding position, this rotation is transmitted to the holding member 29 via the drive gear train 61, as shown in FIG. As shown, the holding member 29 rotates from the intermediate holding position to the second holding position. Accordingly, the second blade portion 72 of the holding member 29 blocks the optical path from the light emitting portion 76 of the PI sensor 30 to the light receiving portion 77 (not shown in FIG. 12), and the PI sensor 30 performs the first detection result. (Low) is output to the controller 91. In this case, the control unit 91 determines that the holding member 29 is in the second holding position.

  As described above, the control unit 91 determines the position of the holding member 29 based on the combination of the rotation direction of the single drive source 60 and the detection result of the single PI sensor 30. Therefore, the fixing device 18 can be simplified, reduced in cost, and reduced in size.

  In addition, the PI sensor 30 including the light emitting unit 76 and the light receiving unit 77 constitutes a detection unit, and a first optical path from the light emitting unit 76 to the light receiving unit 77 is blocked while the holding member 29 is in the first holding position. The holding member 29 is provided with a blade portion 71 and a second blade portion 72 that blocks an optical path from the light emitting portion 76 to the light receiving portion 77 in a state where the holding member 29 is in the second holding position. By adopting such a configuration, it is possible to reliably detect whether or not the holding member 29 is in the first holding position or the second holding position with a simple configuration.

  When the holding member 29 rotates from the intermediate holding position to the first holding position, the first blade portion 71 presses the first moving member 31 and the first moving member 31 rotates from the first retracted position to the first blocking position. When the holding member 29 rotates from the intermediate holding position to the second holding position, the second blade portion 72 presses the second moving member 32 and the second moving member 32 rotates from the second retracted position to the second blocking position. Is configured to do. By adopting such a configuration, the first blade portion 71 and the second blade portion 72 for detecting the position of the holding member 29 are used together as a portion for pressing the first moving member 31 and the second moving member 32. It becomes possible.

  Further, the restriction gear 65 has only a range from a portion engaging with the idle gear 64 when the holding member 29 is in the first holding position to a portion engaging with the idle gear 64 when the holding member 29 is in the second holding position. Gear teeth 68 are provided. Therefore, it is possible to reliably suppress the holding member 29 from rotating beyond the original rotation range.

  The heater 24 is disposed on the inner diameter side of the fixing belt 22, and the first moving member 31 and the second moving member 32 are provided so as to be rotatable along the inner peripheral surface of the fixing belt 22. By adopting such a configuration, the space on the inner diameter side of the fixing belt 22 can be effectively used as an arrangement space for the heater 24, the first moving member 31, and the second moving member 32.

  The fixing device 18 further includes a pressing member 26 that presses the fixing belt 22 toward the lower side (the pressure roller 23 side), and a support member 27 that supports the pressing member 26. By adopting such a configuration, the heat capacity of the fixing device 18 can be reduced.

  In the present embodiment, the case where the holding member 29 is rotated from the intermediate holding position to the first holding position when the temperature of the end region 46 of the fixing belt 22 reaches the reference temperature T has been described. On the other hand, in another different embodiment, when the paper passing through the fixing nip N is switched from the second size paper to the first size paper, the holding member 29 is rotated from the intermediate holding position to the first holding position. May be. That is, the position of the holding member 29 may be controlled based on the temperature of the end region 46 of the fixing belt 22 or may be controlled based on the paper size.

  In the present embodiment, the case where the first and second locking portions 41 and 42 are provided in the insertion hole 40 of the front end plate 37Fr has been described. On the other hand, in other different embodiment, you may provide the 1st, 2nd latching | locking parts 41 and 42 in parts other than the insertion hole 40 of the front end plate 37Fr, and the 1st, 1st in members other than the front end plate 37Fr. Two locking portions 41 and 42 may be provided.

  In this embodiment, the case where the first size paper is used as the paper that is not the maximum size paper has been described. However, in another different embodiment, the maximum size paper may be used as the first size paper. In this case, the end region 46 of the fixing belt 22 is a region through which no size paper passes.

  In this embodiment, the case where the heater 24 is disposed on the inner diameter side of the fixing belt 22 and the first and second moving members 31 and 32 rotate along the inner peripheral surface of the fixing belt 22 has been described. On the other hand, in another different embodiment, the heat source such as the heater 24 is disposed on the outer diameter side of the fixing belt 22, and the first and second moving members 31 and 32 rotate along the outer peripheral surface of the fixing belt 22. You may do it.

  In the present embodiment, the case where the holding member 29 and the first and second moving members 31 and 32 are rotated has been described. However, in another different embodiment, the holding member 29 and the first and second moving members 31 and 32 may be rotated. One or both may move linearly.

  In the present embodiment, the case where a halogen heater is used as the heater 24 has been described. However, in another different embodiment, a ceramic heater or the like may be used as the heater 24.

  In this embodiment, the case where the configuration of the present invention is applied to the fixing device 18 that presses the fixing belt 22 downward (on the pressure roller 23 side) with the pressing member 26 has been described. In the embodiment, the configuration of the present invention may be applied to a fixing device 18 that rotates the fixing belt 22 together with one or a plurality of rollers disposed on the inner diameter side of the fixing belt 22.

  In this embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine. It is also possible.

1 Printer (image forming device)
18 Fixing Device 22 Fixing Belt 23 Pressure Roller (Pressure Member)
24 Heater (heat source)
26 Pressing member 27 Supporting member 29 Holding member 30 PI sensor (detection unit)
31 1st moving member 32 2nd moving member 45 Central area | region (1st area | region)
45a (center area) upper end (the part closest to the heater)
46 End region (second region)
46a (end area) upper end (the part closest to the heater)
Reference Signs List 60 drive source 65 regulating gear 68 gear teeth 71 first blade portion 72 second blade portion 76 light emitting portion 77 light receiving portion 84 first coil spring (first elastic member)
87 Second coil spring (second elastic member)
91 Control unit N Fixing nip

Claims (10)

A fixing belt comprising: a first area through which a recording medium of a first size passes; and a second area provided outside the first area;
A pressure member that presses against the fixing belt to form a fixing nip; and
A heat source that radiates radiant heat toward the fixing belt;
A first block that blocks radiation heat from the heat source toward the portion closest to the heat source in the second region without blocking radiation heat toward the portion closest to the heat source in the first region from the heat source. Between a blocking position and a first retraction position that does not block radiant heat from the heat source toward the portion of the first region that is closest to the heat source and the portion of the second region that is closest to the heat source. A first moving member provided to be movable at
A second blocking position for blocking radiant heat from the heat source toward a portion of the first region closest to the heat source and a portion of the second region closest to the heat source; and from the heat source to the first A second moving member provided movably between a portion of the region that is closest to the heat source and a second retreat position that does not block radiant heat toward the portion of the second region that is closest to the heat source. When,
A first holding position for holding the first moving member at the first blocking position and a second holding member at the second retracted position; and a first holding member at the first retracted position. A fixing device comprising: a holding member movably provided between the second moving member and a second holding position that holds the second moving member at the second blocking position.   The holding member holds the first moving member at the first retracted position and holds the second moving member at the first holding position when the holding member is at an intermediate holding position between the first holding position and the second holding position. 2. The fixing device according to claim 1, wherein the fixing device is held at a retracted position. A drive source capable of rotating forward and reverse to rotate the holding member;
A first detection result is output when the holding member is at either the first holding position or the second holding position, and a second detection result is output when the holding member is at the intermediate holding position. A detector to output;
When the detection unit outputs the first detection result with the drive source rotated in the forward direction, it is determined that the holding member is in the first holding position, and the drive source is rotated in the reverse direction. When the detection unit outputs the first detection result in the state of being held, it is determined that the holding member is in the second holding position, and when the detection unit outputs the second detection result, The fixing device according to claim 2, further comprising: a control unit that determines that the holding member is in the intermediate holding position. The detection unit is a PI sensor including a light emitting unit and a light receiving unit,
The holding member is
A first blade portion that blocks an optical path from the light emitting portion to the light receiving portion in a state where the holding member is in the first holding position;
The fixing device according to claim 3, further comprising: a second blade portion that blocks the optical path from the light emitting portion to the light receiving portion in a state where the holding member is in the second holding position. . When the holding member rotates from the intermediate holding position to the first holding position, the first blade portion presses the first moving member, and the first moving member moves from the first retracted position to the first blocking position. Go to
When the holding member rotates from the intermediate holding position to the second holding position, the second blade portion presses the second moving member, and the second moving member moves from the second retracted position to the second blocking position. The fixing device according to claim 4, wherein the fixing device is moved to the position. A first elastic member connecting the first blade portion and the first moving member;
A second elastic member that connects the second blade part and the second moving member;
When the holding member rotates from the first holding position to the intermediate holding position, the first blade portion pulls the first moving member via the first elastic member, and the first moving member becomes the first Move from the blocking position to the first retracted position;
When the holding member rotates from the second holding position to the intermediate holding position, the second blade portion pulls the second moving member via the second elastic member, and the second moving member becomes the second. The fixing device according to claim 5, wherein the fixing device moves from a blocking position to the second retracted position. An idle gear connected to the drive source;
A restriction gear connected to the holding member and meshing with the idle gear,
The restriction gear includes only a range from a portion that meshes with the idle gear when the holding member is in the first holding position to a portion that meshes with the idle gear when the holding member is in the second holding position. The fixing device according to claim 3, wherein gear teeth are provided. The heat source is disposed on the inner diameter side of the fixing belt,
The fixing device according to claim 1, wherein the first moving member and the second moving member are rotatably provided along an inner peripheral surface of the fixing belt. . A pressing member that presses the fixing belt toward the pressing member;
The fixing device according to claim 1, further comprising a support member that supports the pressing member.   An image forming apparatus comprising the fixing device according to claim 1.

Images